* Force cast on some values before doing arithmetic
Some devices (like Delta InsightPower G3 Mini SNMP Card) return STRING instead of numerical value.
A few lines after, when doing a division on it, everything go bad ( / $divisor).
I added force casting, no more crash and the values are OK.
* Using helper cast_number() instead of intval()
* Fix style
* Add test data
* Stop using deprecated function cast_number
c030b0c00e